Mast cells and T lymphocytes, two cell types integral to development of an allergic response and asthma, express numerous inflammation- generating receptors coupled to heterotrimeric G proteins (GPCRs). The purpose of this study is to understand mechanisms of intracellular G- protein-coupled signal transduction in these cells and subsequent pathways to inflammation. In particular, the project focuses on the control of G protein activity in inflammatory processes by a novel family of regulators of G protein signaling (RGS proteins), which inhibit G alpha subunits by increasing their GTPase activity. G alpha subunits oscillate between GDP- (inactive) and GTP-(active) bound forms. The GTPase accelerating (GAP) activity of RGS proteins limits the time of interaction of active G-alpha and its effectors, resulting in desensitization of GCPR signaling. Despite a growing body of knowledge concerning the biochemical mechanisms of RGS action, almost nothing is known about the physiological role of these proteins in native mammalian systems.RGS4, a GAP expressed highly in mouse brain, heart, and hematopoietic cells, was found also to be expressed in murine mast cells. RGS4 null mice are being generated. A novel role of RGS4 in secretory trafficking was identified through an interaction with the protein COP1 complex. COP1 is a protein multimer thought to be required for maintenance of Golgi structure and formation of some secretory transport carriers. RGS proteins interact with the subunit Beta prime-COP through a conserved dilysine motif and inhibit the normal association of COP1 with Golgi membranes. RGS1, 3, and 4 were shown to inhibit chemotaxis and pro-adhesive responses induced by chemokines in a B lymphoma cell ine. RGS16 was shown to be abundant in T lymphocytes activated with interleukin-2 whereas RGS2 was downregulated in these cells. RGS16, in contrast to results with other RGS proteins, was shown to enhance T cell line chemotactic responses to chemokines. Transgenic mice overexpressing RGS16 in T lymphocytes were generated. An uncharacterized protein expressed highly in lung tissue, RGS13, was cloned and expressed. - GTP, G proteins, RGS proteins, signal transduction, knockout mice, secretory trafficking